The choice between investing in a 10-year Treasury note and a 10-year Treasury Inflation Protected Security presents an interesting dilemma. The TIPS bond pays a much lower current yield than the Treasury note, but the value of a TIPS will be adjusted for inflation. The difference between the two yields indicates the value the bond markets put on the inflation protection provided by a TIPS bond.
The current yields for a 10-year Treasury note and a 10-year TIPS can be found on the Treasury.gov website under "Resource Center" and then under "Interest Rate Statistics." The TIPS rates will be found under "Daily Treasury Real Yield Curve Rates," and the regular Treasury rates are titled "Daily Treasury Yield Curve Rates." The Federal Reserve Bank of St. Louis website provides historical data in graph form if you want to visualize historic yield spread.
TIPS yield data goes back to the start of 2003 and since that point in time, the spread between the two Treasury bonds has mostly remained in a range of 2 to 2.75 percent difference between the two yields. From the start of the data through January 2013, the spread has never exceeded the 2.75 percent high-end of the range. However, it has dipped out of the low side, sometimes dramatically, during periods when the financial market was in turmoil, such as the financial crisis of 2008.
The yield spread between the 10-year Treasury and the TIPS bond can be viewed as the bond market's expectation for inflation as measured by the Consumer Price Index. Since the value of the TIPS is adjusted to match changes in the CPI, if the inflation prediction is accurate, both bonds should provide the same return over the 10-year term. Of course, rates, yields and inflation change over time, so the current spread is a snapshot of the market expectations and that number can and will change.
In late 2008 and early 2009 at the height of the financial crisis, the yields on TIPS spiked upward and the 10-year yield dropped sharply. Right at the beginning of 2009, the two rates were less than 1/4th of a percent apart. After the crises abated the spread again widened to historical norms. About half-way through 2011, the 10-year Treasury yield dropped below 2.5 percent and to maintain the 10-year to TIPS spread, the yield on the 10-year TIPS turned negative. The negative TIPS yield was still in effect in the early months of 2013.